1. Field of The Invention
The present invention relates to switches designed to protect circuits that use a multiplicity of battery cells connected in series for aerospace applications. In particular, the present invention relates to cell bypass switches which can sense a battery cell failure and automatically provide an alternate path around the failed cell, thereby bypassing the failure and allowing the remainder of the battery system to continue its function.
2. Description of The Prior Art
Part of the problem which the present invention addresses is that usually a multiplicity of battery cells are connected in series in a battery system for aerospace applications. When one of the battery cells fails, the whole battery system stops functioning. A single battery cell failure will open the series circuit and the remaining battery cells within the circuit will stop operating. This is where the present invention comes into play.
The following ten (10) prior art patents were uncovered in the pertinent field of the present invention.
1. U.S. Pat. No. 299,970 issued to Fenner on Jun. 10, 1884 for "Automatic Fire Alarm" (hereafter "the Fenner Patent"). PA0 2. U.S. Pat. No. 2,235,766 issued to Knaack on Mar. 18, 1941 for "Thermal Alarm" (hereafter "the Knaack Patent"). PA0 3. U.S. Pat. No. 3,038,042 issued to Hall et al. on Jun. 5, 1962 for "Impact-Operable Electric Alarm Switch Devices" (hereafter "the Hall Patent"). PA0 4. U.S. Pat. No. 3,155,800 issued to Denton on Nov. 3, 1964 for "Single Action Temperature Sensitive Electrical Switch Including Camming Means For A Plunger Retaining Member" (hereafter "the Denton Patent"). PA0 5. U.S. Pat. No. 3,761,856 issued to Mantelet on Sep. 25, 1973 for "Thermal Warning Or Protection Device" (hereafter "the Mantelet Patent"). PA0 6. U.S. Pat. No. 4,075,448 issued to Seedoff et al. on Feb. 21, 1978 for "Cell Bypass Switches For Electrochemical Cell System" (hereafter "the Seedoff Patent"). PA0 7. U.S. Pat. No. 4,390,763 issued to Hruda on Jun. 28, 1973 for "Electrochemical Cell Shunting Switch Assembly With Matrix Array Of Switch Modules" (hereafter "the Hruda Patent"). PA0 8. German Patent No. 429,788 (hereafter "the '788 German Patent"). PA0 9. German Patent No. 1,056,715 (hereafter "the '715 German Patent"). PA0 10. Soviet Patent No. 1,141,468 (hereafter "the Soviet Patent").
The Fenner Patent discloses an automatic fire alarm. It utilizes a soft solder for retaining a spring biased rod. The solder is fusible at a low degree of heat. In the event of a fire, the solder will melt and release the rod which in turn is urged by the spring and presses on two electrical contacts to make them connected to actuate an alarm.
The Knaack Patent also discloses a thermal alarm. It utilizes a fusible element or pellet for regulating the movement of a spring biased transverse rod. The transverse rod has a sloping end face which is engaged with a spring biased longitudinal rod. In the event of overheating, the pellet becomes melted and allows the transverse rod to travel, which in turn releases the longitudinal rod. The movement of the longitudinal rod causes two electrical terminals to contact and thereby trigger an alarm.
The Hall Patent discloses an impact-operable electric alarm switch. It provides a mechanism for making electrical contact upon sudden impact or collision.
The Denton Patent discloses a single action temperature sensitive electrical switch which includes a camming means for a plunger retaining member. The switch has a cylindrical housing wherein a spring biased plunger can travel longitudinally to either make or break electrical connection between two electrical terminals mounted at one end of the cylindrical housing. The movement of the plunger is restrained by a V-shaped spring retainer member. The spring retainer member has two elongated legs. The two legs are held in place by a pellet located at the other end of the cylindrical housing. When the pellet is melted under heat, the spring retainer member is freed, which in turn allows the plunger to travel to make or break electrical connection between the two electrical terminals.
The Mantelet Patent discloses a thermal warning or protection device. The device utilizes a fusible washer for restraining a spring biased contact element. When the washer is melted under heat, the contact element will break the electrical contact between the two electrical terminals.
The Seedoff Patent discloses an electrochemical cell circuit utilizing vacuum interrupter cell bypass switches for preventing impurities from interfering with the switch operation.
The Hruda Patent discloses an electrochemical cell shunting switch assembly with matrix array of switch modules. It is used with a high continuous D.C. current electrochemical cell system for electrically shunting or by-passing a failed cell of the system.
The '788 German Patent discloses a device wherein a pair of arms are utilized for holding the nose of a pin which is biased by a spring. The pair of arms are connected to a sleeve which is also biased by a spring.
The '715 German Patent discloses a fuse device comprising a heating coil arrangement. The fuse device also has a movable spring biased pin which is secured by a solder element.
The Soviet Patent discloses a thermosensitive electrical circuit cut-out device. The Soviet device has two spring biased movable contacts and a solder element. When the solder element is melted, the two spring biased movable contacts quickly disengage the electrical connection of the circuit.
It can be seen that although various melt or pellet elements have been utilized in the prior art patents, almost all of the prior art heat sensitive devices are operating under direct external heat sources, and none of them has taught an electrical conducting solder wire for utilizing electrical current as the source to heat up the wire so that it will be melted to initiate the action of the plunger. In addition, none of the prior art has disclosed the feature of using collapsible collet fingers which upon the withdrawal of the plunger can pass through an elongated narrow channel to release the pin contact for making an electrical contact.
Therefore, it is highly desirable to have a very efficient and also very effective design and construction of a cell bypass switch which is used to protect circuits that utilize a multiplicity of battery cells connected in series.